The advantage that Rust's GTK bindings have over Rust's Qt bindings is great enough to counteract any advantage that Qt has over GTK. That's because GTK has an (XML?) schema that allows bindings and documentation to be autogenerated to a large extent. Binding to Qt from Rust is in comparison very difficult (not to mention the fact that Qt's idiosyncratic programming model naturally conflicts with Rust's militant ownership concepts).
Edit: To be clear, I'm not comparing the relative merits of different GUI options, I'm saying that GTK is the only option that you really have in Rust today.
As I mentioned in another comment, I value my GUIs feeling native on my KDE desktop (and not having to reinvent things like QSettings and, last time I tried with GTK+ 2.x, drag-and-drop multi-select for list views) strongly enough that I start with PyQt and then add rust-cpython and Rust if enough of the application can be cleanly encapsulated away from the GUI code to justify the added build-time complexity.
Edit: To be clear, I'm not comparing the relative merits of different GUI options, I'm saying that GTK is the only option that you really have in Rust today.